Signaling system



- Nov. 25, 1924. 1,516,518

J. R. CARSON SIGNALING SYSTEM Filed July '7, 1920 INVENTOR ATTORNEY Patented Nov. 25, 1924.

UNITED STATES PATENT OFFICE.

JOHN R. CARSON, OF MONTCLAIR, NEW JERSEY, ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

SIGNALING SYSTEM.

Application filed July 7, 1920.

T 0 all whom it may concern:

Be it known that I, JOHN R. Carson, residing at Montclair, in the county of Essex and State of New Jersey, have invented certain Improvements in Signaling Systems, of which the following is a specification.

This invention relates to signaling systems and particularly to means associated with long signaling circuits to reduce the magnitude of interfering currents set up by extraneous causes to the lowest value consistent with the maintenance of a specified speed of transmission of signals.

Signaling waves transmitted over long signaling circuits such as submarine cable circuits are subjected not only to great dis tortion and attenuation by the circuit itself, but they are also liable to interference from sources usually extraneous to the cable itself which sets up within the circuit impulses of such magnitude as to drown out the received signaling wave. This is especially true where the interfering disturbance is set up within the cable at a point near the receiving end of the cable because the disturbance is not attenuated to the same degree as the signaling wave which travels the entire length of the cable.

The distortion and attenuation of signaling waves may be corrected by the use of distortion correction networks in combination with the thermionic amplifier, as shown in the copeuding application of Carson, Se rial No. 240,631, filed June 18, 1918. One of the shortcomings of such an arrangement lies in the fact that both the signaling com ponent and also the disturbing component of the received wave are amplified. If the disturbing component is stronger. as frequently it may be if the source of the interference is not remote from the receiving end, it will, when amplified, be so much greater in magnitude than the amplified signaling component as to render impracticable the reading of the received signal.

It is the object of this invention to provide a suitable selective network adapted to prevent the passage therethrough of disturbing component and at the same time to effect the minimum interference to the passage of the signaling wave.

This invention will be understood from the following description when read in connection with the attached drawing, which Serial No. 394,509.

shows one form of embodiment of the invention.

In the figure 1 represents a submarine cable which is connected with one end of the winding 2 of the transformer 3, to the other end of which winding is connected the artificial line 5 which is adapted to balance the cable 1. Connected with the mid-point of the winding 2 is a conductor 6 by means of which the transmitting apparatus is connected to the cable to provide duplex operation. A second winding, l, of the transformer 3 is connected with the input side of the interference suppression network A which is adapted to substantially eliminate the interference impulses, but at the same time to transmit therethrough the signaling wave without affecting, to any substantial degree, the signaling speed of the received signal wave. The output side of the network A is connected with the input side of the arrangement B, the function of which is to correct the signaling wave for the distortion created therein by the transmission over the cable circuit. The network illustrated at B is of the type shown in the pending Carson application, Serial No. 2l0,(33l, filed June 18, 1918, but it is to be understood that the invention is not limited to the use of this particular distortion correction network but that other networks adapted to perform the same function might be used. The output side of the arrangement. 13 is connected to the circuit containing the receiving apparatus which may he of the well known type including for example, a relay and some form of recording instrument.

The network A comprises a plurality of unilateral devices 7, 10, 13, 16 and 19, the function of which is to prevent interaction between the subnetworks of which the circuit of network A is composed. Each of the subnetworks comprises a capacitance 8, 11, 14, 17 and 20, in combination respectively wtih a resistance 9, 12, 15, 18 and 21. The various subnetworks are separated from each other and also from the inductance 4 and the network B by means of the aforesaid unilateral devices. Although five subnetworks have been shown in the drawing, it is to be understood that the number is not so limited but that any number may be used depending upon the nature of the interferonce against which the receiving apparatus network A the said wave will be amplified by the vacuum tube 7 and will be impressed across the subnetwork comprising the capacitance 8 and the resistance 9. The effect of this network is to transmit with slight in'ipedance the signaling frequencies and to tend to suppress the higher frequency impulses which 'epresent the dis turbance. The resultant wave is then impressed across the input side of the amplifier 10, with the output circuit of which are connected the capacitance 11 and the resistance 12. This latter network is adapted in similar manner to transmit readily the sigi'ialing frequencies and to tend to eliminate the higher frequency steep-sloped wave which represents the interference. It will be seen that by transmitting the impressed wave through a number of networks that the interference component will be substantially eliminated but that the signaling component as attenuated and distorted by propagation over the sulnnarine cable will pass through the network A and be impressed upon the distortion correction arrangement 13. The distorted wave will be amplified by the amplifier B and by means of the. network shown associated therewith there will be derived and combined the received wave and its first and second derivatives. The restored signal wave, free from interference will then be impressed upon the receiving apparatus.

From the foregoing it will be seen that there has been provided in connection with the distortion correction arrangement shown in the said Carson application a network which is adapted to co-operate with the said distortion correction network to eliminate the effects of interference upon the signaling wave before any attempt is made to restore the distorted signaling wave to its transn'iitted form.

Although this invention has been disclosed as embodied in a certain form it is apparent that it is capable of embodiment in other and different forms within the scope of the appended claims.

\Vhat is claimed is:

1. In a signaling system the combination with a circuit characterized by great attenuation and distortion and exposed to interference from extraneous sources of a receiving circuit comprising an interference suppression network adapted to minimize the transmission therethrough of the interference component of the wave impressed upon the said receiving circuit, a distortion correction network adapted to restore substantially the signaling component of the impressed wave to its transmitted form and receiving apparatus adapted to have the said reform wave impressed thereon.

2. In a signaling system the combination with a submarine cable circuit having impressed thereon a wave comprising a signal ing component and an interference component of a receiving circuit comprising a filter adapted to prevent the passage there through of the interference component of the arrival wave, a distortion correction device adapted to restore the signaling component of the arrival wave substantially to its transmitted wave shape and receiving apparatus.

In a signaling system the combination with a submarine cable circuit of a receiving circuit comprising an interference elimination network and a distortion correction network, the said interference elimination network having a plurality of subnetworks each comprising a unilateral device having internal resistance R a condenser of capacitance C and resistance R bridged in parallel across the output side of the said device whereby interference may be prevented without diminishing the signaling R +11 speed provided the ratio 1s greator than the ratio represented by three times the number of subnetworks divided by the period of time required for the arrival wave to reach the amplitude for the required signaling speed.

4-. In a signaling system the combination with a circuit characterized by great distor tion and attenuation and having impulses induced therein by external sources of a receiving circuit comprising an interference eliminating arrangement having a thermionic amplifier of internal resistance R and a condenser of capacitance C and a resistance R bridged in parallel across the output side of the said amplifier whereby the interfering impulsesmay be eliminated provided the ratio ol' i FR R ratio represented by three times the number of stages of ai'nplification divided by the period required for the arrival wave to reach the amplitude required for signaling speed.

5. In a signaling system, the combination with a line circuit of a plurality of lowpass filters, a plurality of unilateral devices inserted between the adjacent filters, a distortion correction network and a unilateral device inserted between the said correction network and the last lowpass filter, the cor rection network comprising an inductance in series with a resistance, and a condenser connected across the output side of the said unilateral device.

(3. In a signaling system, the combination with a line circuit of a plurality of low-pass filters, a plurality of unilateral devices in sorted between adjacent filters, adistortion corrcction network, and an amplifier con nected between the said correction network and the last low-pass filter the said correcs greater than the tion net-Work including); an ihduoteiiee in so ries Wliill a resistiinire, and a, condenser hridged across the output side of the suit aii'ipliiier, the said condenser being; paralleled h u eeeond resistance.

'7. 'iThe method of improving the true-5+ mission of ei gnzilingg; currents over a circuit adapted to (retort th Shape o i the signals and also adapted to have set up therein intertering currents from external source, wiieh consists in receiving; the siguuliug and the iiiter'feri currents, producing; the first derivative oi the r ceived eurrei'ite pziesing those currents hm'iiog :1 frequency heloiv u predeteriiiined limit uud suppr ,iiig those above, amplifying; the currents passed, producing the integral and the second derivm tive of the amplified eulrents and combining); those with the said first derivative to reform the signal.

8. The method of in'iproriugr the transmission of signaling currents over :1 circuit adapted to distort the shape of the signals and also :uhipted to have set up therein interierino currents from external sources which consists in receiving the sig'uzilinr' and the interfering; currents, producing; the first derivative of the received eiirreuts passing those currents having 2 frequency below it predetermined limit and suppressing thosezihove, amplifying; the currents pziesed, protllltlllfi' the integral and the second. (l B]'i\ ZiTQ oi the amplified (illl'l.(%i.t combining these ii'itl'i the said first derivative to reform the signal. and producing; an. iudicotion of the said signal 9. The method oi? improving; the {HHS- illlflOn oi signaling currents over a circuit adapted. to distort the shape of the signals; und also adapted to have set up therein interfering currente from external sources which consists in receiving :i plurality oil? iiireqiieueies repreeeutiue a signaling impulse and on interfering; wave, suppressing the ij'reoueneies of the inte 'riue; Wave and pit iiig; the frequencies ot the signal, amplifying the signal "frequencies, reforming}; the ehape of the signal impulse, and producing an, indication of the signal as reformed" In testimony whereof, I have signed my nature to this specification this day of July, 1920.

JOHN ht. CARSON. 

